Ocean pCO2 Variability and Drivers at the US Atlantic Coastal Pioneer Array

Abstract:

The ocean plays a significant part of the global carbon cycle, by taking up approximately one quarter of all anthropogenic carbon emissions. Characterizing oceanic and atmospheric CO₂ flux is therefore vital for studying climate change and ocean acidification, but the magnitude, sign, and drivers of this flux vary seasonally and spatially. Here we examine 2016-2017 CO₂ flux, variability, and drivers from the US Atlantic continental shelf using three surface moorings (Inshore, Central, and Offshore) in the Ocean Observatories Initiative’s Pioneer Array. Oceanic pCO₂ ranged from 300-500 μatm. Our results show that the Northwest Atlantic acts as a slight source for atmospheric carbon in the late summer starting in July (maximum positive flux from the ocean 2 mmol m-2 d-1), and a large sink the rest of the year (minimum of -14 mmol m-2 d-1 ). The annual average flux was calculated to be -0.85 to -1.6 mol m-2 y-1 between the different moorings and years. From May to September the fluxes are very similar between moorings and years, but they diverge by 1-4 mmol in the fall and winter between moorings, even within the same year. The seasonal variability observed at all stations follows expectations for a thermally driven system but the pCO₂ signal is significantly dampened by non-thermal drivers (likely biological); the two factors act in opposition to diminish a strong seasonal cycle. These results contribute to an existing set of literature addressing Northwest Atlantic coastal CO₂ cycling and flux, and can help establish a baseline comparison for future studies. Long term data collection and further quality control through the Ocean Observatories Initiative will allow research to progress on the effects of climate change and ocean acidification in this area.